/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.solr.update.processor;

import org.apache.solr.core.SolrCore;
import org.apache.solr.schema.IndexSchema;
import org.apache.solr.schema.FieldType;
import org.apache.solr.schema.SchemaField;
import org.apache.solr.schema.TextField;
import org.apache.solr.schema.StrField;

import org.apache.solr.common.SolrInputField;
import org.apache.solr.common.util.NamedList;
import org.apache.solr.request.SolrQueryRequest;
import org.apache.solr.response.SolrQueryResponse;

import org.apache.commons.lang.StringUtils;

/**
 * Concatenates multiple values for fields matching the specified conditions
 * using a configurable <code>delimiter</code> which defaults to "
 * <code>, </code>".
 * <p>
 * By default, this processor concatenates the values for any field name which
 * according to the schema is <code>multiValued="false"</code> and uses
 * <code>TextField</code> or <code>StrField</code>
 * </p>
 * 
 * <p>
 * For example, in the configuration below, any "single valued" string and text
 * field which is found to contain multiple values <i>except</i> for the
 * <code>primary_author</code> field will be concatenated using the string "
 * <code>; </code>" as a delimeter. For the <code>primary_author</code> field,
 * the multiple values will be left alone for
 * <code>FirstFieldValueUpdateProcessorFactory</code> to deal with.
 * </p>
 * 
 * <pre class="prettyprint">
 *  &lt;updateRequestProcessorChain&gt;
 *    &lt;processor class="solr.ConcatFieldUpdateProcessorFactory"&gt;
 *      &lt;str name="delimiter"&gt;; &lt;/str&gt;
 *      &lt;lst name="exclude"&gt;
 *        &lt;str name="fieldName"&gt;primary_author&lt;/str&gt;
 *      &lt;/lst&gt;
 *    &lt;/processor&gt;
 *    &lt;processor class="solr.FirstFieldValueUpdateProcessorFactory"&gt;
 *      &lt;str name="fieldName"&gt;primary_author&lt;/str&gt;
 *    &lt;/processor&gt;
 *  &lt;/updateRequestProcessorChain&gt;
 * </pre>
 */
public final class ConcatFieldUpdateProcessorFactory extends
		FieldMutatingUpdateProcessorFactory {

	String delimiter = ", ";

	@SuppressWarnings("unchecked")
	@Override
	public void init(NamedList args) {
		Object d = args.remove("delimiter");
		if (null != d)
			delimiter = d.toString();

		super.init(args);
	}

	@Override
	public UpdateRequestProcessor getInstance(SolrQueryRequest req,
			SolrQueryResponse rsp, UpdateRequestProcessor next) {
		return new FieldMutatingUpdateProcessor(getSelector(), next) {
			protected SolrInputField mutate(final SolrInputField src) {
				if (src.getValueCount() <= 1)
					return src;

				SolrInputField result = new SolrInputField(src.getName());
				result.setValue(StringUtils.join(src.getValues(), delimiter),
						src.getBoost());
				return result;
			}
		};
	}

	@Override
	public FieldMutatingUpdateProcessor.FieldNameSelector getDefaultSelector(
			final SolrCore core) {

		final IndexSchema schema = core.getSchema();
		return new FieldMutatingUpdateProcessor.FieldNameSelector() {
			public boolean shouldMutate(final String fieldName) {

				// first check type since it should be fastest
				FieldType type = schema.getFieldTypeNoEx(fieldName);
				if (null == type)
					return false;

				if (!(TextField.class.isInstance(type) || StrField.class
						.isInstance(type))) {
					return false;
				}

				// only ask for SchemaField if we passed the type check.
				SchemaField sf = schema.getFieldOrNull(fieldName);
				// shouldn't be null since since type wasn't, but just in case
				if (null == sf)
					return false;

				return !sf.multiValued();
			}
		};
	}

}
